A skin of a fuselage of an aircraft is formed of a thin member called a skin panel (for example, refer to Patent Document 1). In recent years, a technology for integrally forming a broader skin panel than before with using fiber-reinforced resin composite materials (hereinafter, simply referred to as “composite materials”) has been developed. For example, even though a skin panel in the vicinity of the center of the fuselage of a large aircraft has a cylindrical shape, the technology integrally forms a seamless skin panel of a cylindrical shape.
In order to manufacture the skin panel of a cylindrical shape described above, multiple sheets of prepreg, each being prepared by impregnating textiles, such as carbon fiber, with semi-cured thermosetting resin (epoxy resin, etc.), are laminated to be formed into a cylindrical shape (hereinafter, one obtained by laminating multiple sheets of prepreg is referred to as a “laminate”), and the laminate is then put under pressure and heat so as to be cured. At this time, it is important to perform the curing in a state in which the surface of the laminate is kept in tight contact with a mold (generally called “curl plate” or “cowl plate”) having a smooth surface so that a product, produced as a result of the curing, would have a smooth surface. This is because an outside surface of the skin panel comes into contact with an air current, and requires high smoothness.